API ReferenceText to Speech

Create Speech

Synthesize speech audio from text or SSML. Returns the complete audio file plus billing and speech-mark metadata in a single JSON response. For low-latency playback or long-form text, use POST /v1/audio/stream. Set output_format for explicit sample-rate/bitrate control (e.g. pcm_16000 or ulaw_8000 for telephony).

Authentication

AuthorizationBearer

Enter your API key with the Bearer prefix, e.g. ‘Bearer sk_…’.

Headers

Speechify-VersionstringOptional

Request

This endpoint expects an object.
inputstringRequired<=2000 characters

Plain text or SSML to be synthesized to speech. Refer to https://docs.speechify.ai/docs/api-limits for the input size limits. Emotion, Pitch and Speed Rate are configured in the ssml input, please refer to the ssml documentation for more information: https://docs.speechify.ai/docs/ssml#prosody

voice_idstringRequired

Id of the voice to be used for synthesizing speech. Refer to /v1/voices endpoint for available voices

audio_formatenumOptionalDefaults to wav
The format for the output audio. Note, that the current default is "wav", but there's no guarantee it will not change in the future. We recommend always passing the specific param you expect.
languagestringOptional

Language of the input. Follow the format of an ISO 639-1 language code and an ISO 3166-1 region code, separated by a hyphen, e.g. en-US. Please refer to the list of the supported languages and recommendations regarding this parameter: https://docs.speechify.ai/docs/language-support.

modelenumOptionalDefaults to simba-english

Model used for audio synthesis. simba-english is optimized for English, simba-multilingual for non-English or mixed input. simba-3.2 is the streaming-native model with lower TTFB and richer expressivity, and the recommended Simba 3 model. simba-3.0 is the earlier Simba 3.0 model, still available. simba-3.0 and simba-3.2 are currently English only; multilingual coming soon, and non-English voices return 400 until it ships.

optionsobjectOptional
GetSpeechOptionsRequest is the wrapper for request parameters to the client
output_formatenumOptional

The output audio format as a codec_sampleRate_bitrate string. Takes precedence over audio_format when set.

Response headers

X-Request-IDstring
Unique identifier for this request, present on every response (2xx and non-2xx alike). If the caller sends an `X-Request-ID` request header the server echoes it back (sanitized and length-capped) so one logical request can be traced end-to-end; otherwise the server generates a fresh value. Log it on every response and quote it in support requests - it is the stable handle that ties your observation to Speechify's server-side logs, and it matches the `request_id` field in the error envelope.
RateLimit-Limitinteger

Request-rate budget: the maximum number of requests in the current window (the bucket capacity). The IETF-draft un-prefixed name; the legacy alias X-RateLimit-Limit carries the same value. Rides every response.

RateLimit-Remaininginteger

Request-rate budget: requests left in the current window. Legacy alias: X-RateLimit-Remaining.

RateLimit-Resetinteger

Request-rate budget: integer delta-seconds until the window fully refills (same unit as Retry-After). Legacy alias: X-RateLimit-Reset.

Response

Synthesized speech audio for the requested input.
audio_datastringformat: "byte"

Synthesized speech audio, Base64-encoded

audio_formatenum
The codec of the audio data
billable_characters_countlong
The number of billable characters processed in the request.
speech_marksobject
It is used to annotate the audio data with metadata about the synthesis process, like word timing or phoneme details.
output_formatenum

The full codec_sampleRate_bitrate format, echoed back when the request set output_format.

Errors

400
Bad Request Error
401
Unauthorized Error
402
Payment Required Error
403
Forbidden Error
404
Not Found Error
429
Too Many Requests Error
500
Internal Server Error
502
Bad Gateway Error
503
Service Unavailable Error